Which of the following concepts is enforced by certifying that email communications have been sent by
who the message says it has been sent by?

A.
Key escrow

B.
Non-repudiation

C.
Multifactor authentication

D.
Hashing

Explanation:
Regarding digital security, the cryptological meaning and application of non-repudiation shifts to mean:
A service that provides proof of the integrity and origin of data.
An authentication that can be asserted to be genuine with high assurance.
Incorrect Answers:
A: Key escrow addresses the possibility that a third party may need to access keys. Under the conditions
of key escrow, the keys needed to encrypt/decrypt data are held in an escrow account (think of the term
as it relates to home mortgages) and made available if that third party requests them.
C: A multifactor authentication method uses two or more processes for logon. A twofactor method might
use smart cards and biometrics for logon.
D: A hash function is used to map digital data of variable size to digital data of fixed length. A hash
function is not used to verify the sender of an e-mail.

Dulaney, Emmett and Chuck Eastton, CompTIA Security+ Study Guide, 6th Edition, Sybex, Indianapolis,
2014, pp. 133, 255, 262, 414